MusicReasonRooms, Monitoring, and Acoustic Calculations
Which resonant frequencies does this room predict?
Enter length, width, and height. This tool calculates the axial, tangential, and oblique modal frequencies an ideal rigid rectangular room of that size would produce, as a starting point, not a measurement of your actual room.
Answer
Want to learn more? Room Modes and Low-Frequency Behavior
Understand
An axial mode involves reflections between one pair of parallel surfaces, a tangential mode involves two pairs, and an oblique mode involves all three; axial modes are usually the strongest and most audible in practice. A real room is never a perfectly rigid, empty rectangle: furniture, openings, and wall construction all shift a real room's response away from this ideal prediction. This tool never claims to represent your measured room response, prescribe a specific treatment, or provide an acoustic diagnosis.
Worked example
A room 5 m long, 4 m wide, and 3 m high at a speed of sound of 343 m/s has its lowest axial mode along the length at 34.3 Hz, from (343/2) × sqrt((1/5)^2) = 34.3. Doubling every dimension of the room halves every one of its modal frequencies; swapping the stated length and width leaves the set of predicted frequencies unchanged, since the formula only depends on the set of dimensions, not which one is labeled length versus width.
Method and limitations
The tool enumerates integer index triples (nx, ny, nz) from 0 through your chosen maximum, excluding (0,0,0), and computes each frequency with f = (c/2) × sqrt((nx/L)^2 + (ny/W)^2 + (nz/H)^2). A mode with exactly one nonzero index is axial, two is tangential, and three is oblique. Results are sorted by their full-precision frequency and grouped for display only when two modes fall within 0.05 Hz of each other. The default speed of sound, 343 m/s, is a stated assumption you can edit, not a fixed constant for every room's actual air temperature and humidity.
Reading the mode table
Two or more index triples can land on the same, or nearly the same, frequency; a square or near-square room produces more of these coincidences than an irregular one, which is one reason acousticians generally recommend against exact 1:1 or simple whole-number ratios between a room's dimensions. When several modes cluster tightly, their combined effect at that frequency tends to be stronger than any single mode acting alone, which is worth knowing before choosing where to place a listening position or a bass trap. The indices (nx, ny, nz) in the table are counts of half-wavelengths fitting along each axis: a higher index means a higher-order mode, generally weaker and more localized in the room than the lowest axial modes.
This calculator does not model absorption, furnishings, door and window openings, or non-rectangular geometry, all of which shift a real room's measured response away from this ideal prediction. Use it to understand which frequency ranges are likely to need attention before you measure, not as a substitute for an actual in-room measurement.